Continuous output pump

ABSTRACT

A pump for delivering a continuous or uniform i.e., not pulsating, flow of liquid through a flexible tubing. A pump body is provided with an annular recess open at one axial end face thereof, and the body is rotatably mounted on a drive shaft. A sleeve is rotatably connected on axially adjacent camming elements on the drive shaft, and one sleeve axial end face extends into the pump body annular recess. A flexible tubing enters the annular recess and extends therearound for a length greater than one circumferential length of the recess, in particular exiting from the body through the same opening through which it enters. One end of the tubing is connected to a source, for example a reservoir of anticoagulant liquid, and the other end to a load, such as a catheter inserted into the arm of a patient and operatively connected to a pressure transducer.

United States Patent [72] Inventors Daniel T. Hindman Kenmore; Karl A.Baake, Angola, both of, N.Y. [211 App]. No. 873,244 [22] Filed Nov. 3,1969 [45] Patented June 15, 1971 [73] Assignee Menneu-GreatbatchElectronics, Inc.

Clarance, N.Y.

[54] CONTINUOUS OUTPUT PUMP 6 Claims, 13 Drawing Figs.

[52] US. Cl. 417/476, 128/214 [51] Int. Cl ..F04b 43/08, F04b 43/12,A61m S/00 [50] Field of Search 417/476, 474, 475, 477; 418/45 [56]References Cited UNITED STATES PATENTS 2,002,862 5/1935 Moran 417/4762,249,806 7/1941 Bogoslowsky 418/45 2,789,514 4/1957 Hill 417/4762,818,815 1/1958 Corneil 418/45 FOREIGN PATENTS 484,479 5/1938 GreatBritain 417/476 Primary Examiner-Carlton R. Croyle Assistant ExaminerR.E. Gluch Att0rney-Christel and Bean ABSTRACT: A pump for delivering acontinuous or uniform i.e., not pulsating, flow of liquid through aflexible tubing. A pump body is provided with an annular recess open atone axial end face thereof, and the body is rotatably mounted on a driveshaft. A sleeve is rotatably connected on axially adjacent cammingelements on the drive shaft, and one sleeve axial end face extends intothe pump body annular recess. A flexible tubing enters the annularrecess and extends therearound for a length greater than onecircumferential length of the recess, in particular exiting from thebody through the same opening through which it enters. One end of thetubing is connected to a source, for example a reservoir ofanticoagulant liquid, and the other end to a load, such as a catheterinserted into the arm of a patient and operatively connected to apressure transducer.

PATENTEUJUMSIQYI 3584.983

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CONTINUOUS OUTPUT PUMP BACKGROUND OF THE INVENTION This inventionrelates generally to the pump art, and more particularly to a new anduseful pump of the type wherein the material being pumped is transferredthrough a resilient tubing by a nutating member applying compressivepressure to the tubing.

Pumps of this general type are well established and the use of resilienttubing has many advantages in the transfer of liquids. The relativelyeasy removal of the tubing from the pump assembly for sterilizationorreplacement is of great importance in the medical field and wherevercontamination must be prevented. Since the liquids do not come intocontact with metal parts, particular attention to the corrosivetendencies of these parts is unnecessary and ordinary, low costmaterials can be used in the assembly.

A characteristic of pumps of this type heretofore available is apulsating delivery, from the pump, of the material being transferredthrough the tubing. There are, however, applications in which there isneeded a pump of this general type but which will deliver a constant oruniform output flow. One such application is in the medical procedure ofheartbeat monitoring wherein the pump would be employed to supply salinesolution to a catheter inserted into the patient and to which catheter apressure transducer is connected for operating an electrical indicatingor display instrument. If the pump output were not continuous butinstead pulsating, the pulsations in the flow caused by the pump wouldgive rise to electrical signals which can distort or add confusion tothe signals indicative of true heartbeat.

Along with providing a constant or uniform output flow, the pump whenused in heartbeat monitoring procedures should be capable of operatingover a reasonably large pressure range. This is because the equipmentwill be used to sense arterial pressure at one time and veneous pressureat another which pressures are ofcourse significantly different.

In addition to satisfying these two specific requirements, a pump ofthis general type, no matter what its particular use or construction,should be designed to prevent drag by the nutating member on theflexible tubing. Otherwise such frictional dragging will destructivelywear the tubing and will cause the tubing to crawl or creep during thepumping operation, to an extent such that the tubing often will becomeseparated from the pump assembly. The design for preventing destructionwear and creeping" nevertheless should allow easy removal andreplacement of the tubing, especially when the pump is to be used inmedical procedures.

SUMMARY OF THE INVENTION It is therefore a primary object of the presentinvention to provide a pump for delivering a continuous output flow andof the type wherein the material being pumped is transferred through aresilient tubing by a nutating member applying compressive pressure tothe tubing.

It is a further object of this invention to provide such a pump whereindestructive wear and creeping" of the flexible tubing is prevented in amanner allowing easy manual replacement and removal of the tubing.

The present invention provides a pump having a stationary body with anannular recess therein and a nutating member having an annular end facewhich extends into the recess thereby defining an annular region. Asingle length of flexible tubing enters the region, and the length oftubing in the annular region is greater than one circumferential lengthof the region by an amount such that during one complete rotation of thepump drive shaft, a portion of the length of tubing in the region alwayswill be compressed by an amount sufficient to prevent any reverse flow.The nutating member is rotatably connected to the pump drive shaftwhereby destructive wearing of the tubing is minimized and creeping"thereof is prevented.

The foregoing and other advantages and characterizing features of thepresent invention will become clearly apparent from the ensuing detaileddescription of a preferred embodiment thereof taken in conjunction withthe included drawing wherein:

BRIEF DESCRIPTION OF THE DRAWING FIGURES FIG. 1 is a schematic diagramshowing a pump of the present invention as it would appear in use in oneillustrative application;

FIG. 2 is an elevational view of the pump of the present invention;

FIG. 3 is an end view thereof taken about on line 3-3 in FIG. 2;

FIG. 4 is a longitudinal sectional view taken about on line 4-4 in FIG.2;

FIG. 5 is an end view thereof taken about on line 5-5 in FIG. 4;

FIGS. 6 and 7 are end and side elevational views, respectively, of onepart of the drive shaft of the pump of the present invention;

FIG. 8 is a fragmentary view, partly in section, taken about on line 8-8in FIG. 2 but on an enlarged scale and with flexible tubing assembled inthe pump;

FIG. 9 is an enlarged, fragmentary sectional view illustrating thenutating movement of a component of the pump of the present invention;

FIGS. 10:: and 10b, taken about on line 10-10 in FIG. 8, are fragmentaryviews, partly in section, showing release and compression, respectively,of flexible tubing by the pump of the present invention; and

FIGS. 11a and 11b show schematically the manner of assembling flexibletubing in prior art pumps and in the pump of the present invention,respectively.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT FIG. I showsschematically a pump 10 constructed in accordance with the presentinvention as it would appear in use, for example in combination withheartbeat monitoring equipment. The detailed structure of pump 10 willbe described further on in the specification. Suffice it to say at thepresent time, and referring to both FIGS. 1 and 2, that pump 10comprises a generally cylindrical body portion 11 provided with anannular recess 12 open at one axial end face thereof and provided withan opening 13 through the wall thereof communicating with annular recess12. Pump 10 further comprises a drive shaft 14 rotatably mounted in pumpbody 11 by means of a bearing and disposed so that the axis thereof iscoincident with the axis of body 11. In addition, pump 10 includes asleeve 16 mounted on drive shaft 14 for nutating movement about the axisof shaft 14 and at an axial position thereon such that one end of sleeve16 extends partially into annular recess 12 so as to define an annularregion therein. By virtue of this arrangement, upon rotation of driveshaft 14 sleeve 16 is nutated about the axis thereof with the resultthat the volume of the annular region thus defined is varied from amaximum to a minimum in a direction around the circumferential lengththereof. Pump 10 also comprises a single length of flexible tubing 17extending through opening 13 in the wall of pump body 11 and around theannular region therein. The length of tubing 17 in the annular region isgreater than one circumferential length of the region by an amount suchthat during one complete rotation of drive shaft 14, a portion of thelength of tubing 17 in the region always will be compressed by an amountsufficient to prevent any reverse flow through tubing 17. By way ofspecific example as shown in FIG. 1, tubing 17 extends twice around theannular region and thus both enters and leaves pump body 11 through thesingle opening 13. Pump body 11 is fixedly positioned by a supportingframework, designated generally at 18 in FIG. I, r by other suitablemeans, and drive shaft 14 can be driven by an electric motor 19operatively connected thereto and energized by a suitable power supplyindicated generally at 20.

A distinguishing characteristic of pump provided by the presentinvention is that it delivers a continuous or uniform i.e., notpulsating, flow in tubing 17. One particularly ad vantageous use of thepresent invention is in medical heartbeat monitoring procedures. Suchprocedures include the insertion of a catheter into an artery or vein ofa patient and the utilization ofa pressure transducer in communicationwith the catheter to transform blood pressure variations indicative ofheartbeats into electrical signals which, in turn, are displayed orrecorded by readout equipment operatively connected to the transducer. Aproblem frequently arising during these procedures is coagulation ofblood in the catheter which, of course, makes further monitoringimpossible with the catheter in that condition. In order to preventcoagulation, the conventional procedure has been for a doctor or nurseto inject periodically a quantity of saline solution into the catheter,the solution serving as an anticoagulant. This procedure, of course,requires time which can be considerable when a large number of patientsare being monitored over an extended period.

FIG. 1 shows pump 10 provided by the present invention as it is used todeliver a continuous flow of anticoagulant liquid to the catheter andthus obviate the need for hospital personnel to periodically attend thecatheter. The portion of tubing 17 which provides an input to pump 10 isconnected to a tank or reservoir 21 filled with saline solution or otheranticoagulant liquid. The remaining portion of tubing 17 which deliversthe output of pump 10 is in fluid communication with a catheter 22inserted in a patients arm. Catheter 22 is operatively connected to apressure transducer indicated schematically at 23 which, in turn, isoperatively connected through line 24 to conventional readout equipmentdesignated generally at 25. Transducer 23 typically is ofthe typewherein a pressure sensitive diaphragm changes the electrical resistanceof a bridge network. Readout equipment 25 can include, for example, anoscilloscope display.

Pump 10 is driven by motor 19, which preferably is a variable speed DCmotor and brushless for the purpose of avoiding noise, at a speedsufficient to follow a pressure in the patients blood streamcorresponding to one milliliter of mercury. If the patients bloodpressure increases, pump 10 has the capability of following thatpressure. Actually, pump 10 can be constructed so as to follow apressure up to about that equivalent to I000 milliliters of mercurywhich is well beyond pressures encountered in both veneous and arterialpressure sensing. In particular, veneous pressure is known to beequivalent to about I milliliter of mercury and arterial pressure toabout 250 milliliters of mercury. Because of the fact that pump 10follows the patients pressure but does not exceed it, there is no needfor the provision of any additional pressure balancing arrangements.

In the system shown in FIG. 1, pump 10 functions to deliver a continuousor constant flow of saline solution from reservoir 21 through tubing 17to catheter 22 at the rate of about l2 milliliters per hour. It isimportant to note that the flow is continuous, not pulsating. Apulsating flow would activate transducer 23 periodically in addition tothe activation provided by the heartbeats of the patient. This, in turn,would give rise to additional electrical signals either added to orinterspersed between signals produced in response to the patientsheartbeat with the result that the indication from readout equipment 24would become confused and distorted. Pump 10 of the present invention,by virtue of its delivery ofa continuous, nonpulsating output, preventsany confusion or distortion in the indication of the patients heartbeat.Furthermore, any reverse flow of saline solution, i.e. in a directionfrom catheter 22 to pump 10, is prevented by the structural relationshipbetween tubing 17 and pump 10.

FIGS. 2-11 show in detail the specific structure of pump 10 of thepresent invention. Pump body 11, as shown in FIGS. 2-4, is generallycylindrical in shape and can be formed from any suitable material suchas aluminum. A plurality of internally threaded bores 29 can be providedin one axial end face of body 11 for the purpose of attachment to asuitable support such as that designated 18 in FIG. 1. A relativelylarge diameter, central bore 30 is provided through this same end facefor the purpose of receiving a bearing 31, and drive shaft 14 isjournaled therein as seen in FIG. 4. The opposite axial end of body 11,in which annular recess 12 is formed, is provided with a hublike portion32 extending from the innermost wall of recess 12 in an axial directionslightly beyond the point of termination of the outer wall of body 11. Abore 33 is provided in the axial end face of hub 32 through which driveshaft 14 extends. Referring back to FIG. 2, opening 13 includes a firstportion 13a which is slightly elongated in a direction perpendicular tothe axis of body 11 and a second portion 13b disposed parallel to theaxis of body 11 and extending from portion 13a to the axial end face ofthe outer wall of body 11. In other words, the length or extent ofopening 13 in a direction parallel to the axis of body 11 is about equalto the axial length of recess 12.

Sleeve 16 likewise is formed from any suitable material, for examplealuminum, and has an outer diameter slightly less than the diameter ofthe outer surface of annular recess 12 provided in body 11. Sleeve 16has an axial end face 34, shown in FIG. 4, of a radial width orthickness slightly less than the radial width of annular recess 12 inpump body 11. The wall of sleeve 16 defining end face 34 is of constantwidth to a point about midway along the axial length of sleeve 16whereupon it meets a wall 35 disposed perpendicular with respect to theaxis of sleeve 16 and provided with a central bore 36 therein throughwhich pump drive shaft 14 extends. The sleeve wall extending from wall35 through the remaining axial length of sleeve 16 has a slightlysmaller radial width and defines therein a region or chamber 37 whichreceives a bearing 38 for the purpose of mounting drive shaft 14. Theedges of sleeve end face 34 should be smoothed so as to preventdestructive wear of flexible tubing 17 with which it comes in contact.

Pump drive shaft 14 comprises two parts or sections connected togetheras shown most clearly in FIG. 4. The drive shaft part which enters pumpbody 11 from the left-hand side in FIG. 4 includes a rod 42 providedwith threads 43 at one end thereof and connected at the other end in ahollow cylindrical member 44 which is provided with a notch 45 in theend thereof opposite the end in which rod 42 is connected. Notch 45,which is disposed perpendicular to the axis of rod 42, facilitatesconnection of shaft part 40 to the output shaft of a drive means such asmotor 19 shown in FIG. 1.

The part of drive shaft 14 which enters sleeve 16 from the right-handside in FIG. 4 is shown in more detail in FIGS. 6 and 7 and includesfour sections along an axis 50 and having a common axial bore 51therethrough. A first section comprises a knurled knob 52 which isdisc-shaped and concentric with respect to axis 50. A second sectioncomprises a camming element 54 in the form of a generally cylindricalmember having end faces 55 and 56. The cylinder wall is concentric withrespect to axis 50, and end face 55, which abuts an end face of knob 52,is disposed in a plane perpendicular with respect to axis 50. Theopposite axial end face 56 is disposed in a plane which, in turn, isdisposed at a slight acute angle, depending upon the degree of nutationrequired, with respect to a plane perpendicular to axis 50. The degreeof nutation required is dependent upon the diameter of flexible tubing17 and desired flow rate. In the particular example of FIG. 1 with adesired flow rate of l milliliter per hour and with tubing 17 having adiameter of one-eighth inch, end face 56 lies in a plane disposed at anangle of 2 with respect to a plane perpendicular to axis 50.

The drive shaft part includes a third section in the form of cammingelement 57 which likewise is generally cylindrical, having a wall'andend faces 59, 60. To provide the required described, the wall axis isdisposed at an angle of two degrees with respect to axis 50. End face 59is coincident with end face 56 of camming element 54 and this isdisposed in a plane extending at an angle of 2 with respect to a planeperpendicular to axis 50. End face 60 is disposed in a planeperpendicular with respect to axis 50. The drive shaft part is completedby a fourth section in the form of cylinder 61 which is concentric withrespect to axis 50. Internal threads are provided along the portion ofbore 51 common to knob 52 and camming element 54 for engagement withcorresponding threads on rod 42 when the two parts of drive shaft 14 areconnected together.

Pump of the present invention is assembled in the following manner. Thepart of drive shaft 14 located at the left-hand side in FIG. 4, inparticular rod 42, is rotatably positioned in bearing 31 which, in turn,is fixedly mounted in bore 30 of pump body 11. A form of bearing foundto be suitable is commercially available under the designation NICEI6l5DS. This shaft part is oriented relative to body 11 so that rod 42extends through bore 33 in hub 32 so as to expose threads 43. The partof drive shaft 14 shown at the right in FIG. 4 is rotatably mounted insleeve 16 by means of bearing 38 which, in turn, is fixedly mounted inregion or chamber 37 of sleeve 16. A form of bearing 38 foundparticularly suitable is commercially available under the designationNICE I623DE. In particular, camming element 57 is rotatably mounted inbearing 38, and camming element 54 and knob 52 extend axially outwardfrom the axial end face of sleeve 16. Bore 51 of the drive shaft part isin communication with bore 36 of sleeve 16.

Pump body would be fixedly mounted to a suitable support such as thatdesignated 18 in FIG. 1, and cylindrical member 44 of drive shaft 14 isconnected to the output shaft ofa suitable drive means, for examplemotor 19 in FIG. 1. With sleeve 16 and the part of drive shaft 14rotatably mounted therein disconnected from pump body 11 and the otherpart of drive shaft 14, tubing 17 can be assembled .by hand in pump 10in the following manner. A portion of tubing 17 is grasped by hand sothat the longitudinal axis thereof is in a plane generally perpendicularwith respect to the axis of pump body 11. This portion is moved by handin a direction parallel to the axis of body 11 into portion 13b and thenportion 13a of the opening 13. The tubing is positioned around recess 12in pump body 11 and is wound twice around body 11 and then manipulatedfurther by hand so as to leave pump body 11 from portion 13a of opening13.

The manner in which tubing 17 is placed in pump body 11 may beunderstood. more clearly by referring to FIG. 8 which shows tubing 17 infinal assembled condition in pump body 11. It will be noted from aninspection of FIG. 8 that opposite edges of opening portion 13a aredisposed at a slight angle, for example l5, to a line perpendicular tothe axis of pump body 11 and to the plane of opening 13. By virtue ofthis arrangement, tubing 17 is subjected to a more gradual bend as itenters and leaves pump body 11 than would be the case if opening 13included entirely right angle junctions with the inner surface of recess12.

When tubing 17 has been placed in pump body 11, pump 10 is assembledfurther into completed form in the following manner. Sleeve 16 isgrasped and moved toward pump body to a position where the threads 43 ofrod 42 are ready for engagement with the threads in bore 51. A simplemanual rotation of knob 52 then moves sleeve 16 and the drive shaft partcarried thereby axially toward pump body 11 by virtue of the engagementbetween the corresponding threads ofrod 42 and bore 51. The extent ofaxial movement is sufficient so that axial end face 34 of sleeve 16extends partially into recess 12 thereby defining an annular regionwhich contains tubing 17.

Pump 10 of the present invention operates in the following manner. Inresponse to rotation of drive shaft 14, sleeve 16 is nutated about theaxis of shaft 14, as shown in FIG. 9. The angle of nutation, which inthis particular example is 2, is determined by the degree of inclinationof the particular end faces of camming elements 54 and 57 as previouslydescribed. As a result, the annular region definedby'recess 12 in pumpbody 11 and axial end face-of sleeve 16 is varied in volume from amaximum to a minimum in a direction around the circumference thereof.This, in turn, causes a corresponding release and compression offlexible tubing 17 positioned in the annular region as illustratedfurther in FIGS. 10a and 10b.

The manner whereby pump 10 of the present invention delivers a uniformor continuous, not pulsating, output flow is illustrated in FIGS. 11Aand 11B by means of a comparison with prior methods of positioningflexible tubing in a pump of this general type. FIG. 11A showsschematically a length of flexible tubing 70 extending around theannular region in a pump body 71 of this general type for about only onecircumferential length of the region. Arrow 72 indicates the directionalong which tubing 70 is compressed in response to nutating movement ofthe pump member. It will be noted that a discontinuity or open space ispresent along tubing 70 between bends 70a and 70b which correspond tothe exit and entry points, respectively, of tubing 70 in the pump body.More particularly, as tubing 70 is compressed along the directionindicated by the arrow in FIG. 11A by means of the nutating pump member,the portion of tubing 70 near bend 70a is compressed flrst while theportion near bend 70b is in its normally open or relaxed condition.Further travel of the tube contacting portion of the nutating member isacross the gap or space toward the tube portion atbend 70b whereuponthat portion is compressed and the portion near bend 70a is released.Because of the gap or space between bends 70a and 70b, the tube portionnear bend 70a can open from its previously compressed condition beforethe tube portion near bend 70b is compressed. This, in turn, allows aflow through tubing 70 in a reverse direction, i.e. from load to source,relative to the direction desired. The periodic flow reversal causes thepump to deliver a pulsating or nonuniform flow.

FIG. 118 shows schematically the manner in which flexible tubing 17 ispositioned in the pump 10 of the present invention whereby a continuous,nonpulsating output flow is delivered. Flexible tubing 17 is in a singlelength and extends through opening 13 in pump body 11 and around theannular region therein. The length of tubing 17 in the annular region isgreater than one circumferential length of the region by an amount suchthat during one complete rotation of the pump shaft, a portion of thelength of tubing 17 in the region always will be compressed by an amountsufficient to prevent any reverse flow. In other words, tubing 17 enterspump body 11, extends around pump body 11 for a length greater than onecircumferential length of the annular region therein, passing the pointof entry, and exits from pump body 11 at a point positionedcircumferentially beyond the point of entry. As shown in FIG. 11B,tubing 17 preferably is wound around nearly two circumferential lengthsof the annular region in the pump body thus permitting entry and exit ofthe tubing through the same opening in the pump body. As the nutatingmember, specifically pump sleeve 16, moves in the direction of the arrowin FIG. 118, the portion of tubing 17 near bend 17a can open from itspreviously compressed condition before the tube portion near bend 17b isfully compressed. But, the portion of the length of tubing 17 whichextends along the circumferential length of the annular region betweenthe bends 17a and 17b prevents any reverse flow. This is because portion17c will be compressed by sleeve 16 as it travels across the gap orspace between the bends 17a and 17b in tubing 17. As a result, a portionof tubing 17 always will be compressed during each rotation of the pumpshaft thereby preventing any reverse flow of fluid through tubing 17.

In addition to a uniform or continuous output flow, there are severalother significant advantages provided by the construction of pump 10 ofthe present invention. It will be recalled that sleeve 16, the end face34 of which contacts and compresses tubing 17, is rotatably mounted onpump drive shaft 14. In particular, cam element 57 is journaled inbearing 38 which is fixed in region 37 of sleeve 16. The rotatablemounting of sleeve 16 on pump drive shaft 14 minimizes the frictionaldrag between sleeve end face 34 and tubing 17 which otherwise would beofa large amount if sleeve 16 were fixedly mounted on shaft 14. This, inturn, prevents any destructive wear of tubing 17.

The rotatable mounting of sleeve 16 on shaft 14 also prevents "creeping"of tubing 17, in other words movement of tubing 17 along the annularregion in pump body 11. This is because frictional drag between sleeveend face 34 and tubing 17 is minimized. By virtue of this arrangementcreeping" is prevented without the need to anchor tubing 17 in pump 10which would otherwise complicate removal and insertion of tubing 17 inpump 10.

It is therefore apparent that the present invention accomplishes itsintended objects. While a single specific embodiment of the presentinvention has been described in detail, this has been done by way ofillustration without thought oflimitation.

We claim:

1. A pump for delivering a continuous output flow comprismg:

a. a generally cylindrical pump body provided with an annular recessopen at one axial end face thereof and with an opening through the wallof said body communicating with said annular recess;

b. a drive shaft rotatably mounted in said pump body and disposed sothat the axis thereof is coincident with the axis of said annularrecess;

c. a sleeve having an outer diameter slightly less than the diameter ofthe outer surface of said annular recess in said pump body and having anaxial end face of a radial width less than the radial width of saidannular recess, said sleeve being mounted for nutating movement aboutthe axis of said drive shaft and at an axial position thereon so thatsaid sleeve extends partially into said annular recess in said pump bodyso as to define an annular region therein;

d. whereby upon rotation of said shaft said sleeve is nutated about theaxis of said shaft; and

e. a single length of flexible tubing extending through said opening inthe wall of said pump body so as to enter said annular region therein,said tubing extending around said annular region for a length greaterthan one circumferential length of said annular region by an amount suchthat during one complete rotation of said shaft a portion of the lengthof said tubing in said annular region always will be compressed by saidsleeve sufficiently to prevent any reverse flow.

2. A pump as defined in claim 1 wherein the point of exit of said tubingfrom said pump body is positioned circumferentially beyond the point ofentry of said tubing into said pump body.

3. A pump as defined in claim 1 wherein said flexible tubing leaves theannular region in said pump body through the same opening in the wall ofsaid body through which it enters.

4. A pump as defined in claim 1 wherein said sleeve is rotatably mountedon said drive shaft.

5. A pump as defined in claim 1 wherein said drive shaft comprises:

a. a first part rotatably mounted in said pump body; and

b. a second part rotatably mounted in said sleeve and having first andsecond axially adjacent camming elements on which said sleeve isconnected for nutating movement.

6. A pump as defined in claim 5 wherein said first and second driveshaft parts are threadably connected together.

1. A pump for delivering a continuous output flow comprising: a. agenerally cylindrical pump body provided with an annular recess open atone axial end face thereof and with an opening through the wall of saidbody communicating with said annular recess; b. a drive shaft rotatablymounted in said pump body and disposed so that the axis thereof iscoincident with the axis of said annular recess; c. a sleeve having anouter diameter slightLy less than the diameter of the outer surface ofsaid annular recess in said pump body and having an axial end face of aradial width less than the radial width of said annular recess, saidsleeve being mounted for nutating movement about the axis of said driveshaft and at an axial position thereon so that said sleeve extendspartially into said annular recess in said pump body so as to define anannular region therein; d. whereby upon rotation of said shaft saidsleeve is nutated about the axis of said shaft; and e. a single lengthof flexible tubing extending through said opening in the wall of saidpump body so as to enter said annular region therein, said tubingextending around said annular region for a length greater than onecircumferential length of said annular region by an amount such thatduring one complete rotation of said shaft a portion of the length ofsaid tubing in said annular region always will be compressed by saidsleeve sufficiently to prevent any reverse flow.
 2. A pump as defined inclaim 1 wherein the point of exit of said tubing from said pump body ispositioned circumferentially beyond the point of entry of said tubinginto said pump body.
 3. A pump as defined in claim 1 wherein saidflexible tubing leaves the annular region in said pump body through thesame opening in the wall of said body through which it enters.
 4. A pumpas defined in claim 1 wherein said sleeve is rotatably mounted on saiddrive shaft.
 5. A pump as defined in claim 1 wherein said drive shaftcomprises: a. a first part rotatably mounted in said pump body; and b. asecond part rotatably mounted in said sleeve and having first and secondaxially adjacent camming elements on which said sleeve is connected fornutating movement.
 6. A pump as defined in claim 5 wherein said firstand second drive shaft parts are threadably connected together.